Coreus marginatus is a
herbivorous species of
true bug in the family
Coreidae. It is commonly known as the dock bug as it feeds on the leaves and seeds of
docks and sorrels.[1] It is a medium-sized speckled brown insect, between 13 and 15 mm long as an adult, with a broad
abdomen.[2] It occurs throughout
Europe,
Asia and northern Africa.[3] It is often found in dense vegetation, such as
hedgerows and wasteland.
Taxonomy
This species was among the first
Hemipteraformally described in the scientific literature by the Swedish biologist
Carl Linnaeus in 1758, under the name Cimex marginatus.[4] It was transferred to the genus Coreus by the Danish zoologist
Johan Fabricius in 1794.[5] It has numerous
synonyms and was historically placed in the genus Syromastus.
The head,
pronotum and abdomen of an adult dock bug are speckled reddish brown. The
antennae are composed of four segments, red-orange in colour except for the final fourth segment which is black. Between the antennae are two small projections, known as antenniferous tubercles, which can be used to distinguish this species from other superficially similar species.[6] The pronotum has angular upward facing projections and the
scutellum is clearly visible. The rounded edge of the abdomen has lighter coloured markings. Adults are between 13 and 15 millimetres (0.51 and 0.59 in) long and males are typically smaller than females but have longer antennae.
A young (instar II) nymph showing its spiny abdomen and disproportionately large antennaeAn older nymph with distinct abdominal scent glands and visible wingbuds (developing wings)
Young nymphs look different in appearance to the adults. They are heavily spined, less uniform in colouration and have disproportionately large antennae compared to their body size. Older nymphs looks more similar to adults with a more uniform speckled brown colouration but lacking developed wings.
Like other Coreidae, Coreus marginatus has scent glands with small pores in the middle of its
thorax which can release strong-smelling, irritating,
volatile defensive chemicals when disturbed.[7] The pores have an
ultrastructure composed of mushroom-like structures that are connected to each other via ridges and
Trabeculae. The chemical composition of the scent gland secretions is similar between males and females, although the relative proportions are different. In females the most prevalent chemical compound is
hexanoic acid while in males it is
stearic acid.
Distribution
Linnaeus originally described the species from Europe with only one of his specimens having a specific locality of England. Other early specimens collected by
Goeze are from France [8] The current distribution is extensive and covers: Europe, from Portugal to Finland; Asia, from Russia to China; and Africa, known only from Algeria.[3]
Life cycle
Adult male and nymph shown from dorsal and ventral views
Like other Coreidae the dock bug has an annual life cycle consisting of an egg followed by five successive
nymphalinstars before becoming an adult.[6] It
overwinters as an adult and copulates in the typical heteropteran back-to-back position, laying large brown eggs between late May and early July. The eggs take around 3 to 4 weeks to hatch. The young nymphs will feed on leaves and stems while the older nymphs, like the adults, feed on seeds. The nymphs mature to adults from August onwards.
Diet
The dock bug is
herbivorous and feeds on a wide variety of plants from different families. While the common name in English refers to its preferred diet of
docks and sorrels and other plants in the family
Polygonaceae, they also readily feed on certain species of
Asteraceae and
Rosaceae. Adults are known to feed on
raspberry,
gooseberry and sometimes
blackcurrant.[9]
Gallery
Different views and lifestages of Coreus marginatus
Newly hatched nymph of Coreus marginatus showing the comparatively very large antennae
An older nymph showing similar colouration to the adult
Facial view, showing the
rostrum and distinctive orange antennae with black tips.
Coreus marginatus feeding on a plant stem
Lateral view, showing the opening of the scent gland.
References
^Martina Hrušková, Alois Honěk & Stano Pekár; Honěk; Pekár (2005). "Coreus marginatus (Heteroptera: Coreidae) as a natural enemy of Rumex obtusifolius (Polygonaceae)". Acta Oecologica. 28 (3): 281–287.
doi:
10.1016/j.actao.2005.05.004.
^Tristan Bantock & Joseph Botting.
"British Bugs". Retrieved 6 May 2013.
^
abDolling, William (2006), "Family COREIDAE Leach, 1815", in Aukema, Berend; Rieger, Christian (eds.), Catalogue of Heteroptera of the Palaearctic Region, vol. 5, Amsterdam, the Netherlands: The Netherlands Entomological Society, p. 67,
ISBN9071912280
^Livermore, Laurence; Lemaître, Valerie; Dolling, William; Webb, Michael (2013),
Coreoidea Species File Online, retrieved 6 May 2013.
^Moulet, Pierre (1995). Faune de France: Hémiptères Coreoidea (Coreidae, Rhopalidae, Alydidae) Pyrrhocoridae, Stenocephalidae: Euro-Méditerranéens (in French). Vol. 81. Paris: Fédération Française des Sociétés de Sciences Naturelles.